Circuit-controller.



No. 792,110. PATENTED JUNE 18, 1905. J. M. BARR.

CIRCUIT CONTROLLER.

APPLIGATION FILED MAE. 7, 1904.

WITNESSES: INVENTOR ATTbRNEY UNITED STATES Patented June 13, 1905.

PATENT OEEIcE.

JOHN M. BARR, OF NEW' YORK, N. Y., ASSIGNOR TO VESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

CIRCUIT-CONTROLLER.

SPECIFICATION forming part of Letters Patent No. 792,110, dated June 13, 1905,

Application filed March 7, 1904. Serial No, 196,967.

To ('I/ZZ 11/71/0717, i l may concern:

Be it known that 1, JOHN M. BARR, a citizen of the United States, and a resident of New York, in the county of New York and State of New York, have invented a new and useful lmprovem ent in Oircuit-Oontrollers, of which the following is a specification.

My invention relates to protective devices for electric motors; and it has for its object to provide means for preventing injurious sparking and flashing at the brushes of electric motors when they act temporarily as generators.

In the operation of shunt and compound wound variable-speed motors, in which the speed variation is obtained by the application of two or more voltages and by variations in the strength of the shunt-field or by either expedient alone, it has been found that when changing the motor connections from a higher to a lower voltage or when suddenly strengthening the shunt-field of the motor a serious sparking at the commutator occurs on account of the fact that the motor temporarily acts as a generator and delivers current to the supply-circuit.

My invention provides means for automatically inserting resistance in the armaturecircuit of the motor during the periods in which the motor acts as a generator and in this manner eiiectually avoids objectionable sparking at the commutator-brushes.

The single figure of the accompanying drawing represents, diagran'unatically, the motorcircuits of apparatus embodying my invention.

The magnet-core 1 is provided with two windings 2 and 3, the terminals of the former being connected directly to supply-mains 1 and 5 and one terminal of the latter being connected to the supply-main 4 and its other terminal to a contact-block 8. The mains or line conductors 4, 5, and 6 are connected with any suitable source 7 of electrical energy for supplying multivoltage circuits, such as that set forth in the subject-matter of Patent No. 513,006, granted to Michael von Dolivo-Dobrowolsky, the difference of potential between the conductors 4L and 6 being greater than or approximately double that between the conductors 4L and 5 or between the conductors 5 and 6.

A resistance 9 has one terminal connected to the contact-block 8 and its other terminal connected to one terminal of the motor-armature 10. is provided for connecting the other terminal. of the motor-armature 10 to the one or the other of the supply-mains 5 and 6. A contactblock 12 is connected to the same terminal of the motor-armature 10 as is the resistance 9. One end of the magnet-core 1 is provided with a suitable low-resistance contact-brush 13, the ends of which engage the contact-terminals 8 and 12 when the magnet-core is raised by the energized windings 2 and 3. The field-magnet winding 11 of the motor may be connected with any pair of the supply-mains, such as 4 and 6, and any suitable means, such as a switch 15, may be provided for controlling the amount of current supplied thereto.

The windings 2 and 3 may have approximately the same magnetizing power, or the winding 2 may produce a held of slightly greater density than that produced by the coil 3. hen the switch-arm 11 makes contact with the terminal 16, the motor is running at a high speed, because its armature is supplied from the higher voltage -supply mains 1 and 6, and if the switch-arm 11 is moved suddenly to make contact with the terminal 17 the motor-armature will rotate at a speed greater than that corresponding to the voltage supplied from the lower-voltage-supply mains 4E and 5, so that it becomes a generator and delivers current to the supplymains. \Vhile the motor is supplied from the higher-voltage mains 1 and 6, the magnet-core 1 is drawn up so that the brush 13 makes contact with the terminals 8 and 12 and the magnetic fields produced by the coils 2 and 3 act conjointly to retain the magnet-core in this position; but while the motor acts as a generator the current in the coil 3 is reversed, and the magnetic fields produced by the coils 2 and 3 therefore neutralize each other and per- Suitable means, such as a switch 11,

mit the magnet-core 1 to drop under the action of gravity, and thus separate the member 13 from the terminals 8 and 12, so that the motor, acting as a generator, delivers its current to the supply-mains through the resistance 9 and continues to do so until its counter electromotive force is approximately equal to the voltage between the supply-mains 4 and 5,when the magnet-core 1 is again raised and connection is made between the terminals 8 and 12 and the brush 13. The operation of the apparatus is similar to that just described if the motor shunt-field 14: is suddenly strengthened or if for any other reason the motor should act as a generator.

While I have shown and described my in- .vention as primarily applicable to multivoltage systems, it is obvious that it may also be employed in connection with single-voltage systems which embody motors that are liable to operate temporarily as generators, and while I have shown a motor having only a shunt-field-magnet winding it is evident that it may also be provided with a series-fieldmagnet winding.

I desire it to be also understood that any suitable form or type of controlling apparatus may be employed for making the circuit changes that are necessary to secure the results of my invention.

I claim as my invention 1. The combination with an electric motor and means for controllably supplying energy at different voltages thereto, of means for antomatically inserting a suitable resistance in series with the motor when changing from a higher to a lower supply voltage and maintaining the same in circuit while the motor generates a voltage that exceeds the lower supply voltage.

2. The combination with an electric motor and supply-circuits having different voltages, of means for automatically inserting resistance in the motor-circuit when changing from a higher to a lower supply voltage or when the motor-field is suddenly strengthened.

3. The combination with an electric motor and a supply-circuit, of means for automatically inserting resistance in the motor-circuit whenever and while the motor generates a voltage that exceeds the supply voltage.

1. The combination with an electric motor and means for varying its speed, of means for automatically inserting resistance in the motor-circuit whenever and while the motor runs at a higher speed than that corresponding to the voltage of the supply-circuit to which it is connected.

5. The combination with an electric motor and supply-circuits having difl'erent voltages,

of means for automatically inserting resistance in the motor-circuit whenever and while the motor generates a voltage that exceeds the voltage of the motor-supply circuit and comprising a magnet-core provided with a winding in shunt to one of the supply-circuitsand a winding in series with the armature of the motor, a resistance, and means operated by the magnet-core for short-circuiting said resistance.

6. The combination with an electric motor and means for operating the same at different speeds, of a resistance in the armature-circuit of the motor, a switch for normally short-circuiting said resistance, and two controllingwindings for said switch that normally assist each other but which oppose each other when the motor voltage exceeds the supply voltage.

7. The combination with an electric motor and supply-circuits therefor having different voltages, of a resistance in the armature-circuit of the motor, a magnet-core and windings therefor, one connected to one of the supply-circuits and the other in series with the motor-armature, said windings acting conjointly to operate said magnet-core and thereby short-circuit said resistance when energy is supplied to the motor-armature, but acting in opposition to each other so as to insert said resistance in the motor-armature circuit when the motor acts as a generator.

8. The combination with an electric motor and sources of energy of difierent voltages, of a resistance in the armature-circuit of the motor, a switch for normally short-circuiting said resistance, a coil in shunt to one of said sources, a coil in series relation to said motor, and means actuated by both of said coils for closing said switch.

9. The combination with an electric motor and a source of multivoltages, of a resistance and means operated by an excessive motor voltage toinsert said resistance in circuit with the motor-armature when the motor is changed from a higher to a lower voltage circuit.

10. The combination with an electric motor and a suitable source of supply, of a resistance and means for inserting said resistance in circuit with the motor-armature whenever the motor, operating as a dynamo, generates a higher voltage than that which it is receiving.

In testimony whereof I have hereunto sul scribed my name this 13th day of February,

JOHN M. BARR.

Witnesses:

WM. H. CAPEL, THos. H. BROWN. 

